Mathematics I (Calculus) 2075

Question Paper Details
Tribhuwan University
Institute of Science and Technology
2075
Bachelor Level / First Semester / Science
Computer Science and Information Technology ( MTH112 )
( Mathematics I (Calculus) )
Full Marks: 80
Pass Marks: 32
Time: 3 hours
Candidates are required to give their answers in their own words as far as practicable.
The figures in the margin indicate full marks.

Attempt any three questions:

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1. (a) A function is defined by f(x) = |x| , calculate f(-3), f(4), and sketch the graph.

5 marks
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Given,

Now,

Now, for sketching graph  calculating y = f(x) for different values of x

Graph:


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    (b) Prove that the  does not exist

5 marks
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Given

Now,

Here,

Hence,  doesn’t exist.

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2. (a) Find the domain and sketch the graph of the function f(x) = x2 - 6x . 

5 marks
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Given

For domain, for all real values of x, f(x) exist. So, domain is set of all real number i.e. domain is  

For Graph, calculating the values of y = f(x) for different values of x;

Plotting these points on graph we get:


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    (b) Estimate the area between the curve y = xand the lines y = 1 and y = 2. 

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Given

And lines:

y =1, y = 2

The given curve is the parabola and the sketch of the given curve is

Required area 


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3. (a) Find the Maclaurin series for cos x and prove that it represents cos x for all x.

4 marks
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We need to find derivatives of f(x) = cos x, so

Therefore, Maclaurin series for cos x  is

Since the cosine function and all the derivatives of cosine function have absolute value less than or equal to 1. So, by Taylor’s inequality

Now,

i.e.

 for all values of x.

This implies that the series converges to cosx for every value of x.

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    (b) Define initial value problem. Solve that initial value problem of y' + 2y = 3, y(0) = 1.

4 marks
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The problem of finding a function y of x when we know its derivative and its value y0 at a particular point x0 is called an initial value problem.

Given,

Comparing given equation with  we have

P =2 and Q=3

Now,

Applying the initial condition y(0)=1


Applying this value, we have:


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    (c) Find the volume of a sphere of a radius a .

2 marks
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The sphere of radius a can be obtained rotating the half circle graph (semi-circle) of the function

 about the x-axis. 

The volume V is obtained as follows:

by the symmetry about the y-axis,


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4. (a) If  does exist? Justify. 

5 marks
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Here

As  we get  form.

So, set  where m is some constant value then,

Along  we observe  and we get


And at m =1,

Thus,

So, the limit does not exist.

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4(b) Calculate  for  f(x, y) = 100 - 6x2y and  

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Attempt any ten Questions:

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5. If  f(x) =  and g(x) = , find fog and fof. 

5 marks
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Given,

Now,


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6. Define continuity on an interval. Show that the function  is continuous on the interval [ -1,1] . 

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A function f is continuous from the right at a number a if  and f is continuous from the left at a if  .

A function f is continuous on an interval if it is continuous at every number in the interval. If f is defined only one side of an end point of the interval, we understand continuous at the end point to mean continuous from the right or continuous from the left.


Given,


Let  then

Which shows that f(x) is continuous at .

For the end points i.e. x=-1

Which shows that f(x) is continuous at the left end point x = -1

Similarly for the end point x=1

Which shows that f(x) is continuous at the right end point x = 1.

Hence f(x) is continuous at [-1,1]

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7. Verify Mean value theorem of f(x) = x3 - 3x + 2 for [-1, 2].

5 marks
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Given,

f(x) = x3-3x+2 

Since, f(x) = x3-3x+2  is continuous on [-1, 2] and f’(x) = 3x2-3 so, differentiable on (-1, 2).

Thus f(x) = x3-3x+2 satisfy the both conditions for mean value theorem. So, there exist  such that


Clearly, 

Hence, mean value theorem satisfied.

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8. Stating with x1 = 2, find the third approximation x3 to the root of the equation x3 - 2x - 5 = 0. 

5 marks
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Given,

By Newton’s method we have

When x1=2

Then


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9. Evaluate 

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Here

Take,

Put Then  So that


Thus, form (i)


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10. Find the volume of the resulting solid which is enclosed by the curve y = x and y = x2 is rotated about the x-axis.

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11. Find the solution of y'' + 4y' + 4 = 0. 

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Given,

The characteristics equation of given differential equation is

Here the roots are real and equal.

The general solution is


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12. Determine whether the series  converges or diverges. 

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Given,

Here,

Now;

Therefore, by nth term test for divergence, the given series is divergent.

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13. If a = (4, 0, 3) and b = (-2, 1, 5) find |a|, the vector a - b and 2a + b. 

5 marks
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Official Answer

Given

a = (4 , 0, 3)

b = (-2, 1, 5)

Now,

 

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14. Find  and  if z is defined as a function of x and y by the equation x3 + y3 + z3 + 6xyz = 1. 

5 marks
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Given,

Now,

Differentiating w.r.to x

Again,

Differentiating w.r.to y


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15.  Find the extreme values of the function f(x, y) = x2 + 2y2 on the circle x2 + y2 = 1. 

5 marks
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Given,

And, let

By method of Lagrange’s multiplier, for some scalar 

This implies,

This gives

From (ii) we have x = 0 or λ = 1. If x = 0, then (i) gives y = ±1. If λ = 1, then y = 0 from (iii), so then (i) gives x = ±1. Therefore, f has possible extreme values at the points (0, 1), (0, −1) (1, 0), and (−1, 0). Evaluating f at these four points, we find that

f(0, 1) = 2

f(0, −1) = 2

f(1, 0) = 1

f(−1, 0) = 1

Therefore, the maximum value of f on the circle x 2 + y 2 = 1 is f(0, ±1) = 2 and the minimum value is f(±1, 0) = 1.

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